This invention relates to a cab for construction machines, which can be suitably applied, for example, to hydraulic excavators, hydraulic cranes and the like.
Generally, construction machines such as hydraulic excavators, for example, are largely constituted by a lower structure, an upper structure which is rotatably mounted on the lower structure, and a working mechanism which is provided on a front portion of the upper structure for lifting loads up and down. A cab is provided on a revolving frame of the upper structure as an operating room to be occupied by an operator at the control of the machine.
The cabs of hydraulic excavators of this sort are usually formed in a box-like shape, from a standpoint of protecting the operators. As for an example of such cabs for hydraulic excavators, there has been known a cab box construction having mount bases located at four corners of the cab box, base link frames connecting adjacent mount bases to each other in transverse and longitudinal directions of the machine, right and left front pillars erected on right front and left front mount bases, right and left rear pillars erected on right and left rear mount bases, right and left roof pillars connecting upper end portions of the front and rear pillars, a front tie frame connecting upper end portions of right and left front pillars, and a rear tie frame connecting upper end portions of right and left rear pillars (e.g., as disclosed in Japanese Laid-Open Patent Publication No. 2000-198469).
Among hydraulic excavators of various types, those machines which are relatively small in size are usually provided with an upper structure which is reduced in width and length, particularly in length from a front end of a cab to a rear end of a counterweight in order to minimize the radius of revolving of the upper structure for the sake of ensuring higher working efficiency.
However, in addition to a space for a cab, the upper structure of a hydraulic excavator is normally required to have a broad space for mounting various equipments such as engine, heat exchanger, fuel tank, operating oil tank and a group of control valves, and the cab itself is required to have a broad space for installation of various instruments and devices in addition to a dwelling room for an operator. In this regard, with the cab construction as disclosed in the above-mentioned Japanese Laid-Open Patent Publication No. 2000-198469, it is difficult to downsize the upper structure.
In this connection, there have been known hydraulic excavators with a cab which is so arranged as to permit downsizing of an upper structure. Prior art hydraulic excavators with a cab of this sort are described, for example, in Japanese Laid-Open Utility Model Publication No. H5-61246 and S59-102657.
In the case of the prior art cabs in the patent and utility model publications just mentioned, a recess is provided at the back side of a cab box in order to accommodate part of an engine and other equipments therein, and a cab is located in a receded position for the purpose of reducing the size of an upper structure.
Further, in the case of the prior art construction machine cabs disclosed in the above-mentioned Japanese Laid-Open Utility Model Publication No. H5-61246 and S59-102657, rear pillars are bent in a crank-like shape in order to provide a recess at the back side of the cab, making the rear pillars complicate in shape. Therefore, rear pillars of a hollow structure have to be fabricated, for example, by joining and welding inner and outer panel members to each other after pressing the respective panel members to a predetermined shape on a press.
More specifically, the complication in shape of pillars or other structural members, resulting from the provision of a recessed portion in a cab box, makes it necessary to make a plural number of panel members from sheet material by the use of complicate dies and then to fabricate pillars of hollow structures by joining and welding the shaped panel members in an intricate manner. Needless to say, complication of the fabrication process is reflected by lower productivity and higher cost.
In view of the above-discussed problems with the prior art, it is an object of the present invention to provide a cab for a construction machine, which can be fabricated easily at low cost, including fabrication of rear pillars, despite provision of an expanded machine room on the back side of the cab, permitting to improve productivity and at the same time to cut production cost of the cab.
More specifically, the present invention is directed to a cab for construction machines which includes: mount bases located at four corners; base link frames arranged to connect said mount bases in transverse and longitudinal directions of the machine; left and right front pillars erected on left front and right front mount bases; left and right rear pillars erected on left rear and right rear mount bases; left and right roof pillars disposed in the longitudinal direction and bridged between upper end portions of the left and right front pillars and the left and right rear pillars, respectively; a front tie frame bridged between upper end portions of the left and right front pillars to connect same in the transverse direction; and a rear tie frame bridged between upper end portions of the left and right rear pillars to connect same in the transverse direction.
According to the present invention, in order to solve the above-mentioned problems, there is provided a cab for construction machines, which is characterized in that: the left and right rear pillars are each constituted by a hollow steel pipe of a staggered shape with an inclined intermediate pillar portion between upright lower and upper pillar portions to have positions of the lower and upper pillar portions shifted in the forward and rearward directions, respectively; a recessed space is provided on the lower side of the intermediate pillar portions of the left and right rear pillars to expand an external machine room; and a rear expansion space is provided on the upper side of the intermediate pillar portions of the left and right rear pillars to expand an internal dwelling room of the cab.
With the arrangements just described, the rear pillars of complicate shape, having positions of lower and upper pillar portions staggered in forward and rearward directions, can be fabricated simply by forming bends in an intermediate portion of a hollow steel pipe. A recessed space is provided on the lower side of the rear pillars for the purpose of expanding an external machine room, while a rear expansion space is provided on the upper side of the rear pillars to expand a dwelling room within the cab.
According to a preferred form of the present invention, the left and right pillars are each constituted by a lower pillar portion erected on one of rear mount bases, an intermediate pillar portion inclined rearward from upper end of the lower pillar portion, and an upper pillar portion extended upright from upper end of the intermediate pillar portion, the lower, intermediate and upper portions being formed by bending a hollow steel pipe.
With the arrangements just described, the rear pillars of a complicate shape can be fabricated easily by the use of a hollow steel pipe, bending an upper end of the lower pillar portion in the rearward direction and then bending an upper end of the intermediate pillar portion in the forward direction.
According to another preferred form of the present invention, a rear panel is provided between the left and right rear pillars to cover the back side of the cab, the rear panel being formed of a plate shaped in conformity with a staggered profile of the rear pillars.
With the arrangements just described, the rear panel can be attached between the rear pillars easily by welding or other suitable means. When attached in position, the rear panel delimits the fore end of the recessed space along with the rear pillars.
According to still another preferred form of the present invention, the left and right rear pillars are each constituted by a steel pipe of a diversified sectional shape which is obtained by drawing an ordinary round steel pipe.
In this instance, each one of the rear pillars can be constituted by a steel pipe of a diversified sectional shape which is obtained by drawing an ordinary round steel pipe into a specific sectional shape, and bending the steel pipe of a diversified shape into a staggered form. Therefore, the rear pillars can be fabricated very easily even in a case they have a complicate shape in section.
According to a further preferred form of the present invention, a center pillar is provided at one lateral side of the cab and connected to the base link frame and the roof pillar at an intermediate position between front and rear ends of the cab, the center pillar being integrally provided with a side panel portion extending to the rear side in such a way as to cover up the recessed space.
With the arrangements just described, the strength of the base link frame and the roof pillar can be enhanced by the center pillar. Besides, the recessed space can be concealed by the side panel to improve the appearance of the cab.
According to a further preferred form of the present invention, the left and right rear pillars are each provided with a vertically extending window pane fitting protuberance on a transversely inner side for fitting a rear window glass thereon.
With the arrangement just described, rear window glass can be fitted in position very easily by the use of the window pane fitting protuberances which are provided on the left and right rear pillars.
According to a further preferred form of the present invention, a design cover is attached to the back side of the rear panel in such a way as to cover upper side of the recessed space.
With the arrangement just described, the open top side of the recessed space can be covered up by the design cover to improve the appearance of the cab.